What’s that you’re doing, Mr. Kühn?

“I’m checking the control unit that regulates the cabin pressure in an Airbus A350. The air pressure at cruising altitude (around 10 000 meters) is much lower than at sea level, which is why we artificially raise the pressure inside the cabin. For this, fresh air is constantly pumped into the cabin while used air flows out through a valve. The job of the control unit, know as the “outflow valve control unit,” or “OCU,” is to regulate this valve. Sensors and computers transmit a constant stream of data to the OCU, enabling it to calculate whether to open the valve wider to increase the cabin pressure or close it a little more so as to bring the pressure down. Any malfunction of the OCU automatically triggers its integrated back-up system, which means that the safety of our passengers is ensured at all times. The defective OCU is replaced immediately after landing. I inspect it on the test stand you see here, locate the defect – and repair it.”